The invention relates to internal combustion engines with combustion chambers whose walls are partially held at an elevated temperature by preventing the heat transfer to cooler parts of the engine. In known combustion chambers of this type, especially those used in conjunction with antechambers in stratified charge engines, the antechambers are substantially dome-shaped inserts with thin walls which, at low temperatures, maintain an insulating clearance from the cooled combustion chamber walls but which, after being heated, make contact with the cooled combustion chamber walls due to thermal expansion of the material and thereafter permit heat transport away from the chamber to prevent its overheating.
These known systems, however, have an inherently large thermal inertia and thus require a relatively long time to reach the wall temperature which is necessary for optimum mixture preparation after, for example, a cold engine start. Furthermore, they are subject to large temperature fluctuation during the operation of the engine because the thermal inertia permits only incomplete temperature control of the surface of the combustion chamber. This is especially the case during sudden changes of the power output of the engine which may lead to overheating of the combustion chamber walls.
On the other hand, modern experiments have shown that when combustion chamber walls are held at relatively high temperatures, and fuel is injected onto these hot surfaces, the overall smoke emission and hydrocarbon emission of the engine may be significantly reduced.